Power semiconductor device

ABSTRACT

A power semiconductor device includes power semiconductor elements joined to wiring patterns of a circuit substrate, cylindrical external terminal communication sections, and wiring means for forming electrical connection between, for example, the power semiconductor elements and the cylindrical external terminal communication sections. The power semiconductor elements, the cylindrical external terminal communication sections, and the wiring means are sealed with transfer molding resin. The cylindrical external terminal communication sections are arranged on the wiring patterns so as to be substantially perpendicular to the wiring patterns, such that external terminals are insertable and connectable to the cylindrical external terminal communication sections, and such that a plurality of cylindrical external terminal communication sections among the cylindrical external terminal communication sections are arranged two-dimensionally on each of wiring patterns that act as main circuits.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resin-sealed power semiconductordevice, formed by transfer molding, which is excellent in terms ofproductivity. The present invention particularly relates to aresin-sealed power semiconductor device, formed by transfer molding,which is small in size, realizes operation with a large current, and ishighly reliable.

2. Description of the Background Art

A power semiconductor device capable of operating with a large currentand a high voltage, which is able to efficiently discharge heat, whichis generated by the operation of the power semiconductor device, to theoutside of the power semiconductor device, is the one that is formedsuch that: power semiconductor elements are mounted on a substrate thatincludes a metal plate acting as a heat sink and a wiring pattern formedabove the metal plate, the substrate including a ceramic plateinterposed as an insulation layer between the wiring pattern and themetal plate; and heat-hardening resin is cast such that silicone gel ispositioned between the heat-hardening resin and the substrate (see,e.g., Page 3, FIG. 1 of Japanese Laid-Open Patent Publication No.H08-316357 (hereinafter, referred to as Patent Document 1)).

However, in manufacturing of the power semiconductor device described inPatent Document 1, there are processes of, for example: bonding theexternal casing, which is formed of thermoplastic resin, to the metalplate; filling and curing the silicone gel; and injecting and curing theheat-hardening resin. Thus, there are a large number of manufacturingprocesses, causing a prolonged manufacturing time. Accordingly, there isa problem of low productivity.

A power semiconductor device which solves this problem and which isexcellent in terms of productivity is the one in which: lead frames areprovided on a metal plate while an insulation layer is interposedbetween the lead frames and the metal plate; and power semiconductorelements are mounted on the lead frames and sealed with transfer moldingresin (see, e.g., Page 3, FIG. 1 of Japanese Laid-Open PatentPublication No. 2001-196495 (hereinafter, referred to as Patent Document2)).

The power semiconductor device described in Patent Document 2, which issealed with transfer molding resin, has a structure in which lead framesprotrude, as external terminals, from the sides of the sealing resin ofthe transfer molding. Accordingly, there is a problem that it isdifficult to reduce the size of the power semiconductor device. Inaddition, since a bending process is performed on the lead frames thatare used as the external terminals, there is a limitation regarding thethickness thereof. For this reason, the amount of current to be appliedto the external terminals cannot be increased. Thus, there is a problemthat an increase in the current is limited in the power semiconductordevice.

A power semiconductor device sealed with transfer molding resin, whichis small in size and capable of increasing the current to be applied andsolving the above problems, is the one in which: power semiconductorelements such as an IGBT and the like are mounted on a circuit patternjoined to a metal heat sink base; and main terminals and controlterminals for external connection are joined to a circuit patternsurface so as to be substantially perpendicular to the circuit patternsurface, and are transfer molded.

A copper block, a cylinder having a screw hole, or a resin-molded nut,is used for a main terminal connected to a main circuit of the powersemiconductor device. The main terminal that is a copper block is joinedto external wiring by soldering. The main terminal that is a cylinderhaving a screw hole, and the main terminal in which a nut is resinmolded, are connected to external wiring by bolts. Further, a femaleconnector is used as a control terminal to be connected to a controlcircuit of the power semiconductor device, and is connected to externalwiring by a pin-type terminal provided on a control substrate that isthe external wiring.

In the power semiconductor device sealed with transfer molding resin, abus bar to which a large current can be applied is used as the externalwiring to be connected to the main terminal connected to the maincircuit (see, e.g., Page 7 to 9, FIGS. 1, 5 and 10 of Japanese Laid-OpenPatent Publication No. 2007-184315 (hereinafter, referred to as PatentDocument 3)).

In the power semiconductor device described in Patent Document 3 whichis sealed with transfer molding resin, the external wiring, which is abus bar through which a large current can be applied to the mainterminal, is fixed by thread connection or soldering. Accordingly, asubstantial stress is applied to the main terminal area during theassembling of the power semiconductor device. Due to this stress, thereis a problem that defects occur at the main terminal area, for example,a gap occurs at a joint surface between the outer side surface of themain terminal and the transfer molding resin, or fine cracks occur inthe transfer molding resin. This causes problems of low yield, lowproductivity, and low reliability of the power semiconductor device.These problems are more prominent when the connection to the externalwiring is formed by thread connection.

Further, since a large current is applied, even if a cable is used forexternal wiring to be connected to the main terminal, the cable usedherein is highly rigid. Accordingly, the same problems occur.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above problems. Theobject of the present invention is to provide a power semiconductordevice sealed with transfer molding resin, which is capable of, even ifexternal wiring capable of applying a large current is connected to amain terminal connected to a main circuit of the power semiconductordevice, reducing defects that occur at the main terminal area due to theconnection with the external wiring. The provided power semiconductordevice is also high in yield, excellent in terms of productivity, andhighly reliable.

A power semiconductor device according to the present invention includesa circuit substrate including a metal heat sink and including a highthermal conductive insulation layer joined to one surface of the metalheat sink and including wiring patterns provided on a surface of thehigh thermal conductive insulation layer, which surface is opposite to asurface, of the high thermal conductive insulation layer, joined to themetal heat sink; power semiconductor elements joined to the wiringpatterns; cylindrical external terminal communication sections joined tothe wiring patterns; and wiring means for establishing conductionbetween the power semiconductor elements, between the wiring patterns,and between the power semiconductor elements and the wiring patterns.The circuit substrate, the power semiconductor elements, the cylindricalexternal terminal communication sections, and the wiring means are allsealed with transfer molding resin. The cylindrical external terminalcommunication sections are joined to the wiring patterns so as to besubstantially perpendicular to the wiring patterns, such that aplurality of cylindrical external terminal communication sections amongthe cylindrical external terminal communication sections aretwo-dimensionally arranged on each of wiring patterns that act as maincircuits. Holes of the cylindrical external terminal communicationsections, to which external terminals are insertable and connectable,are exposed at a top surface of the transfer molding resin. Since thepower semiconductor device according to the present invention has theabove configuration, the stress, which occurs due to the connection ofthe external terminals to the cylindrical external terminalcommunication sections, can be dispersed and reduced, and defects at thecylindrical external terminal communication sections can be prevented.

Another power semiconductor device according to the present inventionincludes a plurality of AC-side cylindrical external terminalcommunication sections that are arranged two-dimensionally on wiringpatterns, a plurality of DC-side cylindrical external terminalcommunication sections that are arranged two-dimensionally on the wiringpatterns, and power semiconductor elements electrically conductive withthe plurality of AC-side cylindrical external terminal communicationsections and the plurality of DC-side cylindrical external terminalcommunication sections. The plurality of AC-side cylindrical externalterminal communication sections, the plurality of DC-side cylindricalexternal terminal communication sections, and the power semiconductorelements are all sealed with transfer molding resin. The AC-side andDC-side cylindrical external terminal communication sections have holesformed at a top surface of the transfer molding resin. The AC-sidecylindrical external terminal communication sections are connected to anAC-side external terminal. The DC-side cylindrical external terminalcommunication sections are connected to a DC-side wiring substrate. TheAC-side cylindrical external terminal communication sections areconnected to a connection between a negative electrode of apositive-electrode-side power semiconductor element from among the powersemiconductor elements and a positive electrode of anegative-electrode-side power semiconductor element from among the powersemiconductor elements. A plurality of connecting pins to be connectedto the AC-side cylindrical external terminal communication sections aretwo-dimensionally provided in a plate portion of the AC-side externalterminal. The DC-side cylindrical external terminal communicationsections include a plurality of positive-electrode-side cylindricalexternal terminal communication sections and a plurality ofnegative-electrode-side cylindrical external terminal communicationsections. The positive-electrode-side cylindrical external terminalcommunication sections are connected to a positive electrode of thepositive-electrode-side power semiconductor element, and thenegative-electrode-side cylindrical external terminal communicationsections are connected to a negative electrode of thenegative-electrode-side power semiconductor element. The DC-side wiringsubstrate is formed by integrating a positive-electrode-side wiringboard and a negative-electrode-side wiring board with an insulationlayer interposed therebetween, the positive-electrode-side wiring boardbeing connected to the positive-electrode-side cylindrical externalterminal communication sections via connecting pins, and thenegative-electrode-side wiring board being connected to thenegative-electrode-side cylindrical external terminal communicationsections via connecting pins. A plurality of connecting pins to beconnected to the DC-side cylindrical external terminal communicationsections are provided two-dimensionally in a plate portion of theDC-side wiring substrate formed by said integrating. Since this otherpower semiconductor device according to the present invention has theabove configuration, the stress, which occurs due to the connection ofthe external terminals to the cylindrical external terminalcommunication sections, can be dispersed and reduced, and defects at thecylindrical external terminal communication sections can be prevented.In addition, circuit inductance can be reduced, and surge voltage thatoccurs when a large current supply is cut off can be suppressed.

The forgoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plane view showing that transfer molding resin ona circuit substrate of a power semiconductor device according to thefirst embodiment of the present invention, is removed;

FIG. 2 is a schematic cross sectional view of the power semiconductordevice shown in FIG. 1, which is cut along a line A-A indicated in FIG.1 when the transfer molding resin is present on the circuit substrate;

FIG. 3 shows that the power semiconductor device according to the firstembodiment of the present invention is sealed, in a mold, with transfermolding resin;

FIG. 4 is a schematic top view of a power semiconductor device accordingto the second embodiment of the present invention;

FIG. 5 is a schematic cross sectional view of the power semiconductordevice shown in FIG. 4, which is cut along a line B-B indicated in FIG.4;

FIG. 6A is a schematic top view showing an external terminal having fourconnecting pins to be connected to cylindrical external terminalcommunication sections of each main circuit of the power semiconductordevice according to the second embodiment of the present invention;

FIG. 6B is a schematic cross-sectional view which is cut along a lineC-C indicated in the schematic top view of FIG. 6A;

FIG. 7A is a schematic top view showing an external terminal having fourconnecting pins to be connected to cylindrical external terminalcommunication sections of each main circuit of a power semiconductordevice according to the third embodiment of the present invention;

FIG. 7B is a schematic cross-sectional view which is cut along a lineD-D indicated in the schematic top view of FIG. 7A;

FIG. 8 is a schematic top view of a main body of a power semiconductordevice according to the fourth embodiment of the present invention;

FIG. 9 shows a circuit configuration of the main body of the powersemiconductor device according to the fourth embodiment of the presentinvention;

FIG. 10 is a schematic top view of the power semiconductor deviceaccording to the fourth embodiment of the present invention, the mainbody of which includes external wiring to be connected to an externalcircuit; and

FIG. 11 is a schematic cross sectional view of the power semiconductordevice shown in FIG. 10, which is cut along a line E-E indicated in theschematic top view of FIG. 10.

FIG. 12A is a schematic top view showing an inner diameter of a topportion of a cylindrical external terminal communication section greaterthan an inner diameter of a central portion of the cylindrical externalcommunication section.

FIG. 12B is a schematic cross-sectional view which is cut along a lineF-F indicated in the schematic top view of FIG. 12A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION FirstEmbodiment

FIG. 1 is a schematic plane view showing that transfer molding resin ona circuit substrate of a power semiconductor device according to thefirst embodiment of the present invention, is removed.

FIG. 2 is a schematic cross sectional view of the power semiconductordevice shown in FIG. 1, which is cut along a line A-A indicated in FIG.1 when the transfer molding resin is present on the circuit substrate.

As shown in FIGS. 1 and 2, in a power semiconductor device 100 of thepresent embodiment, a metal circuit substrate is used, which is formedsuch that: a resin insulation layer 2 is provided on one surface of ametal heat sink 1; and wiring patterns are provided on a surface of theresin insulation layer 2, which surface is opposite to a surface, of theresin insulation layer 2, joined to the metal heat sink 1. An IGBT 4 anda diode 5 connected in antiparallel with the IGBT 4, which are powersemiconductor elements, are mounted on one of the wiring patterns. Thesepower semiconductor elements are electrically connected to the one ofthe wiring patterns by means of solder 6 or the like. Top surfaceelectrodes of the IGBT 4 and the diode 5 are electrically connected tocorresponding wiring patterns by the wire bonding 7 that is wiringmeans.

Cylindrical external terminal communication sections are joined to thewiring patterns so as to be substantially perpendicular to the wiringpatterns.

To be specific, a first cylindrical external terminal communicationsection 8 a is joined to a first wiring pattern 3 a that is a maincircuit electrically connected to the collector electrode of the IGBT 4and to the anode electrode of the diode 5; a second cylindrical externalterminal communication section 8 b is connected to a second wiringpattern 3 b that is a main circuit electrically connected to the emitterelectrode of the IGBT 4 and to the cathode electrode of the diode 5; athird cylindrical external terminal communication section 8 c is joinedto a third wiring pattern 3C that is a control circuit electricallyconnected only to the gate terminal of the IGBT 4; and a fourthcylindrical external terminal communication section 8 d is joined to afourth wiring pattern 3 d that is a control circuit electricallyconnected only to the emitter electrode of the IGBT 4.

In the power semiconductor device 100 of the present embodiment, thefirst cylindrical external terminal communication section 8 a and thesecond cylindrical external terminal communication section 8 b, whichare connected to the wiring patterns acting as main circuits, eachinclude multiple cylindrical external terminal communication sectionsjoined to corresponding wiring patterns. For example, the firstcylindrical external terminal communication section 8 a includes fourcylindrical external terminal communication sections joined to the firstwiring pattern 3 a, which are arranged two-dimensionally (the term“two-dimensionally” hereinafter means “so as not to all align in thesame axis”) such that two pairs of them form two lines in parallel; andthe second cylindrical external terminal communication section 8 bincludes four cylindrical external terminal communication sectionsjoined to the second wiring pattern 3 b, which are arrangedtwo-dimensionally such that two pairs of them form two lines inparallel.

Whereas, the third cylindrical external terminal communication section 8c and the fourth cylindrical external terminal communication section 8d, which are connected to the wiring patterns acting as the controlcircuits, each include one cylindrical external terminal communicationsection joined to a corresponding wiring pattern.

In the present embodiment, the first cylindrical external terminalcommunication section 8 a and the second cylindrical external terminalcommunication section 8 b each include four cylindrical externalterminal communication sections that are two-dimensionally joined to thecorresponding wiring pattern. However, the number of these cylindricalexternal terminal communication sections to be included is not limitedto 4. The number of these cylindrical external terminal communicationsections to be included may be three or more if the space foraccommodating these cylindrical external terminal communication sectionsallows. To be specific, the number of these cylindrical externalterminal communication sections to be included is preferably 3 to 12.

A structure, which is formed with: the metal heat sink 1; the resininsulation layer 2; the wiring patterns; the IGBT 4; the diode 5; thesolder 6; the wire bonding 7; and the cylindrical external terminalcommunication sections, is sealed with transfer molding resin 9. Here, aheat dissipation surface of the metal heat sink 1, which is an oppositesurface to the surface having the resin insulation layer 2 providedthereon, is not sealed with the transfer molding resin 9. Also, surfacesof the cylindrical external terminal communication sections, which areopposite to surfaces, of the cylindrical external terminal communicationsections, joined to the wiring patterns, are not sealed with thetransfer molding resin 9 (hereinafter, these unsealed surfaces will bereferred to as top surfaces of the cylindrical external terminalcommunication sections). The transfer molding resin 9 is not presentwithin the cylindrical external terminal communication sections. Theabove unsealed surfaces and holes of the cylindrical external terminalcommunication sections are exposed.

Since the power semiconductor device 100 of the present embodiment hasthe structure as described above, the heat dissipation from the heatdissipation surface of the metal circuit substrate is excellent. Inaddition, external terminals, each of which has a pin connectable, bypress-in connection, to a cylindrical external terminal communicationsection that is a metal cylinder and each of which is capable ofperforming metal-to-metal joint, can be used for external wiringelectrically connecting to an external circuit. In particular, the firstcylindrical external terminal communication section 8 a and the secondcylindrical external terminal communication section 8 b, which areconnected to the main circuits to which a large current is applied, eachinclude multiple cylindrical external terminal communication sections.Accordingly, an external terminal having multiple pins can be used foreach of the cylindrical external terminal communication sections 8 a and8 b.

A specific example of an external terminal having multiple pins is a busbar having multiple pins.

In the present embodiment, external terminals are used for the externalwiring. However, metal cables, which can be solder-bonded to thecylindrical external terminal communication sections, may be usedinstead. Since the cylindrical external terminal communication sections8 a and 8 b connected to the main circuits each include multiplecylindrical external terminal communication sections, multiple metalcables are connected to each of the cylindrical external terminalcommunication sections 8 a and 8 b.

Thus, in the power semiconductor device 100 of the present embodiment,external terminals, which are bus bars each having multiple pins, can beused to connect the cylindrical external terminal communicationsections, which are connected to the main circuits, to an externalcircuit. Accordingly, the stress, which is applied to the cylindricalexternal terminal communication sections due to the connection of theexternal terminals, can be dispersed and reduced.

Further, in the case of using metal cables for connecting thecylindrical external terminal communication sections, which areconnected to the main circuits, to an external circuit, multiple metalcables can be used without using thick cables. Accordingly, the stress,which is applied to the cylindrical external terminal communicationsections due to the connection of the metal cables, can be dispersed andreduced.

Still further, the external terminal communication sections arecylinders that do not have screw threads. Accordingly, the connection ofthe external terminals or metal cables to the cylindrical externalterminal communication sections is not thread connection. Therefore, thestress, which occurs due to the connection of the external terminals ormetal cables, is further reduced.

Thus, the stress applied to the cylindrical external terminalcommunication sections is reduced in the power semiconductor device 100of the present embodiment. This eliminates defects of the cylindricalexternal terminal communication sections, such as, an occurrence of agap at a joint surface between the outer side surface of a cylindricalexternal terminal communication section and the transfer molding resin9, or an occurrence of fine cracks in the transfer molding resin 9. Thisrealizes high yield and excellent productivity in manufacturing, andalso realizes excellent reliability.

Further, in the power semiconductor device 100 of the presentembodiment, the cylindrical external terminal communication sections 8 aand 8 b, which are electrically connected to the main circuits, are eachconnected to such external wiring as external terminals or metal cablesthrough multiple cylindrical external terminal communication sections.As a result, large current capacity can be accommodated.

Still further, the power semiconductor device 100 of the presentembodiment has a structure in which the cylindrical external terminalcommunication sections are disposed on the metal circuit substrate thatincludes the metal heat sink 1, the resin insulation layer 2 and thewiring patterns. Accordingly, the positions and the number of thecylindrical external terminal communication sections can be freelyselected by only changing the wiring patterns. Thus, the degree offreedom in determining the number of external wires to be connected andin determining the positions to which the external wires are connected,is very high.

In the present embodiment, a metal having excellent thermalconductivity, for example, aluminum, aluminum alloy, copper, copperalloy, steel, steel alloy, or the like may be used for the metal heatsink 1. Alternatively, a composite material such as a composite ofcopper/steel-nickel alloy/copper, a composite of aluminum/steel-nickelalloy/aluminum, or the like may be used for the metal heat sink 1. Inparticular, in the case of using power semiconductor elements eachhaving a high current capacity, it is preferred to use copper havingexcellent thermal conductivity. The thickness, length and width of themetal heat sink 1 are properly determined based on the current carryingcapacity of each power semiconductor element. That is, the thickness,length and width of the metal heat sink 1 are increased in accordancewith an increase in the current carrying capacity of each powersemiconductor element.

In the present embodiment, used as the resin insulation layer 2 may be,for example, a resin insulation sheet containing various ceramics andinorganic powder, or a resin insulation sheet containing glass fiber.The inorganic powder contained in the resin insulation layer 2 is, forexample, alumina, beryllia, boron nitride, magnesia, silica, siliconnitride, or aluminum nitride. The thickness of the resin insulationlayer is, for example, 20 to 400 μm.

Further, in the present embodiment, for example, a copper foil is usedfor each wiring pattern, and aluminum wires are used for the wirebonding 7. The thickness of the copper foil used for each wiring patternand the diameter of the aluminum wires used for the wire bonding 7 arealso properly determined based on the current carrying capacity of eachpower semiconductor element.

Still further, in the present embodiment, metal cylinders are used forthe cylindrical external terminal communication sections, for example.The material used for the metal cylinders is preferably a metal platedwith, for example, copper, copper alloy, aluminum, or aluminum alloy,which has excellent thermal conductivity and electrical conductivity andwhich can be joined to the wiring patterns by soldering.

The thickness of the cylindrical external terminal communicationsections is set so that the cylindrical external terminal communicationsections may not be crushed due to the molding pressure of the transfermolding. The height of the cylindrical external terminal communicationsections is set to such a height as to allow external terminals, whichare later inserted and connected, to be connected sufficiently. Innerdiameters of the cylindrical external terminal communication sectionsare determined based on outer diameters of inserted portions of externalterminals that are later inserted and connected to the cylindricalexternal terminal communication sections. The inner diameters of thecylindrical external terminal communication sections are set so as toallow, at least, the external terminals to be attached to thecylindrical external terminal communication sections.

The inner diameter of a top portion of each cylindrical externalterminal communication section may be set to be equal, to, or greaterthan, (for example, as shown in FIGS. 12A and 12B), the inner diameterof the central portion of said each cylindrical external terminalcommunication section. In this manner, the external terminals can bereadily inserted into the cylindrical external terminal communicationsections.

Epoxy resin filled with silica powder filler is used as the transfermolding resin 9, for example. In the transfer molding resin 9, thecontent percentage of the filled silica powder is determined to be theoptimal amount in consideration of a thermal expansion coefficient orthe like of each component used in the power semiconductor device.

For example, when copper is used for the wiring patterns and the metalheat sink 1, the amount of silica powder filling the epoxy resin is setsuch that the thermal expansion coefficient of the transfer moldingresin 9 coincides with the thermal expansion coefficient of the copper,that is, 16 ppm/° C. In this manner, a power semiconductor device, inwhich a warp does not occur, can be obtained.

In order to improve heat dissipation of the transfer molding resin, itis preferred to use alumina powder as the filler, instead of silicapowder.

Described next is an example of a manufacturing method of the powersemiconductor device of the present embodiment.

In manufacturing of the power semiconductor device 100 of the presentembodiment, for example, an epoxy resin sheet containing B-stage aluminapowder is placed on a 3 mm-thick aluminum plate, and a 0.3 mm-thickcopper foil is superimposed thereon. Then, the layer of: the aluminumplate; the epoxy resin sheet containing the alumina powder; and thecopper foil, is heated and pressurized so as to join the aluminum plateand the copper foil via the epoxy resin sheet containing the aluminapowder. Next, the wiring patterns are formed by performing etching onthe copper foil.

In this manner, the metallic circuit substrate is formed, whichincludes: the aluminum metal heat sink; the resin insulation layerformed of epoxy resin containing alumina powder; and the copper wiringpatterns.

Next, by using the solder 6, the IGBT 4 and the diode 5 that are powersemiconductor elements are joined to element mounting portions providedat predetermined positions on the wiring patterns, and the cylindricalexternal terminal communication sections are joined to joining areasthat are provided, for the cylindrical external terminal communicationsections, at predetermined positions on the wiring patterns. To bespecific, the IGBT 4, the diode 5 and the first cylindrical externalterminal communication section 8 a are joined to the first wiringpattern 3 a, and the second cylindrical external terminal communicationsection 8 b is joined to the second wiring pattern 3 b. The thirdcylindrical external terminal communication section 8 c and the fourthcylindrical external terminal communication section 8 d, which are to beconnected to the control circuits, are joined to the third wiringpattern 3C and the fourth wiring pattern 3 d, respectively.

Then, between the wiring patterns and the IGBT 4, between the IGBT 4 andthe diode 5, and between the diode 5 and the wiring patterns, positionsthat require conduction therebetween are connected by the aluminum wirebonding 7.

Next, the metal circuit substrate, on which the wire-bonded powersemiconductor elements and the cylindrical external terminalcommunication sections are mounted, is set into a mold and then sealedby a transfer molding method with the transfer molding resin 9 that isof, for example, an epoxy resin type filled with silica powder. In thismanner, the power semiconductor device is completed.

FIG. 3 shows that the power semiconductor device according to the firstembodiment of the present invention is sealed, in a mold, with transfermolding resin.

Hereinafter, a process of sealing the power semiconductor device withthe transfer molding resin will be described in detail with reference toFIG. 3.

First, the power semiconductor device on which the wire bonding processhas been completed is set into a lower mold 11 on which a spot facingprocess has been performed such that the measurement of the spot facingsubstantially coincides with the height of the power semiconductordevice. Next, a resin sheet 12 having no adhesion with the transfermolding resin 9 and having elasticity and having heat resistance thatdoes not cause heat deterioration even at approximately 200° C., isadhered and integrated to an upper mold 10 by vacuuming or the like. Theupper mold 10 to which the resin sheet 12 is adhered is brought intocontact with the lower mold 11, and then mold clamping is performed.Subsequently, a mold cavity formed with the upper mold 10 and the lowermold 11 is filled with the transfer molding resin 9.

The resin sheet 12 to be adhered to the upper mold 10 is, for example, afluorine-type resin sheet such as a Teflon (registered trademark) sheet.

The depth of the spot facing on the lower mold 11 is set such that thecylindrical external terminal communication sections of the powersemiconductor device on which the wire bonding process has beencompleted, slightly dent into the resin sheet 12. The depth of the spotfacing on the lower mold 11 substantially depends on the thickness ofthe resin sheet 12 to be used. Accordingly, for example, if thefluorine-type resin sheet 12 that is 200 μm thick is used, the height,from the heat dissipation surface of the metal heat sink 1, of the topsurfaces of the cylindrical external terminal communication sections maybe formed with a tolerance of approximately 100 μm.

Since the power semiconductor device is transfer molded in the abovemanner, in the power semiconductor device 100 of the present embodiment,the transfer molding resin 9 is prevented from reaching the heatdissipation surface of the metal circuit substrate and the top surfacesof the cylindrical external terminal communication sections, and fromentering the holes of the cylindrical external terminal communicationsections. Also, the heat dissipation surface of the metal circuitsubstrate, the top surfaces of the cylindrical external terminalcommunication sections, and the inner surfaces of the holes, areexposed.

Other than the above-described first method, there are the followingsecond to fourth methods, which are not shown, for performing transfermolding on the power semiconductor device such that the heat dissipationsurface of the metal circuit substrate and the top surfaces and theinner surfaces of the cylindrical external terminal communicationsections are exposed.

The second method requires strict management with respect to, forexample: the height of the components used in the power semiconductordevice and the height of the soldering (precision of a few μm isrequired); the tolerance of the materials; and the processes.Nonetheless, this method further improves the precision of the height,from the heat dissipation surface of the metal circuit substrate, of thetop surfaces of the cylindrical external terminal communicationsections.

In this manner, the transfer molding resin 9 can be prevented fromreaching the heat dissipation surface of the metal circuit substrate andthe top surfaces of the cylindrical external terminal communicationsections, and from entering the holes of the cylindrical externalterminal communication sections.

In the third method, elastic materials are partially provided on: asurface of the lower mold 11, the surface contacting the metal heat sink1; and a surface of the upper mold 10, the surface contacting thecylindrical external terminal communication sections. In this method,operations, such as attaching or detaching these elastic materials, arecomplicated, and every time the size of the metallic circuit substrateor the positions of the cylindrical external terminal communicationsections are changed, the elastic materials to be provided needredesigning.

Still, in this manner, the transfer molding resin 9 can be preventedfrom reaching the heat dissipation surface of the metal circuitsubstrate and the top surfaces of the cylindrical external terminalcommunication sections, and from entering the holes of the cylindricalexternal terminal communication sections.

In the fourth method, the holes of the cylindrical external terminalcommunication sections are filled, in advance, with a filling materialthat has no adhesion with the transfer molding resin 9, and the fillingmaterial is removed after the transfer molding is performed. In thefourth method, the deeper the depth of the cylindrical external terminalcommunication sections, the more complex is the means required forremoving the filling material from the cylindrical external terminalcommunication sections.

Still, in this manner, the transfer molding resin 9 can be preventedfrom reaching the heat dissipation surface of the metal circuitsubstrate and the top surfaces of the cylindrical external terminalcommunication sections, and from entering the holes of the cylindricalexternal terminal communication sections. In particular, the transfermolding resin 9 is readily prevented from entering the holes of thecylindrical external terminal communication sections.

Particularly, the first transfer molding method is able to readilyprevent, even with a low precision of the height of the powersemiconductor device, the transfer molding resin 9 from reaching theheat dissipation surface of the metal circuit substrate and the topsurfaces of the cylindrical external terminal communication sections,and from entering the holes of the cylindrical external terminalcommunication sections.

Further, automatic replacement of the resin sheet 12 provided on theupper mold 10 is possible, and a single mold can accommodate anyvariation of the size of the metal circuit substrate and the positionsof the cylindrical external terminal communication sections. Thisrealizes excellent mass productivity and reduction in the manufacturingcost of the power semiconductor device.

In the present embodiment, the IGBT 4 and the diode 5 are used as powersemiconductor elements. However, the power semiconductor elements arenot limited thereto. For example, a MOSFET, Schottky diode or the likemay be used as a power semiconductor element. In the case of using aMOSFET, it is not necessary to connect the diode in antiparallel withthe MOSFET. Used as a material of the power semiconductor elements maybe not only general silicon, but also wide band gap semiconductor suchas silicon carbide (SiC).

Further, in the present embodiment, the wire bonding 7 is used toconnect the power semiconductor elements and to connect the powersemiconductor elements and the corresponding wiring pattern. That is,the wire bonding 7 is used as wiring means. However, the wiring means isnot limited thereto.

Still further, although a metal circuit substrate is used in the presentembodiment, a ceramic substrate may be used instead. For example, theceramic substrate includes: a ceramic plate that is a high thermalconductive insulation layer; copper wiring patterns provided on onesurface of the ceramic plate; and a copper metal heat sink provided onthe other surface of the ceramic plate.

Second Embodiment

FIG. 4 is a schematic top view of a power semiconductor device accordingto the second embodiment of the present invention.

FIG. 5 is a schematic cross sectional view of the power semiconductordevice shown in FIG. 4, which is cut along a line B-B indicated in FIG.4.

In the present embodiment, a surface of the transfer molding resin 9, atwhich holes of cylindrical external terminal communication sections ofthe power semiconductor device are present, is referred to as a topsurface.

As shown in FIGS. 4 and 5, a power semiconductor device 200 of thepresent embodiment is the same as the power semiconductor device 100 ofthe first embodiment except that in the present embodiment, externalterminals 20 each provided with connecting pins 21 are connected to thecylindrical external terminal communication sections of the powersemiconductor device 100 of the first embodiment. One external terminalconnecting pin 21 is inserted into the cylindrical external terminalcommunication section of each control circuit, and a plurality ofexternal terminal connecting pins 21 are inserted into the cylindricalexternal terminal communication sections of each main circuit.

FIG. 6A is a schematic top view showing an external terminal 20 havingfour connecting pins to be connected to the cylindrical externalterminal communication sections of each main circuit of the powersemiconductor device according to the second embodiment of the presentinvention. FIG. 6B is a schematic cross-sectional view which is cutalong a line C-C indicated in the schematic top view of FIG. 6A.

In the present embodiment, a surface of a plate portion 22 of theexternal terminal 20, which is the opposite surface to a surface havingconnecting pins 21 protruding downward therefrom, is referred to as atop surface.

As shown in FIGS. 6A and 6B, the external terminal 20, which isconnected to each of the cylindrical external terminal communicationsections 8 a and 8 b of the main circuits, includes the plate portion 22and the connecting pins 21. Four connecting pins 21, which are arrangedtwo-dimensionally such that two pairs of them form two lines inparallel, are provided in the plate portion 22 so as to be substantiallyperpendicular to a plate surface of the plate portion 22.

Relay communication holes 23, to which the connecting pins 21 areconnected, are provided on one side of the plate portion 22. An externalcircuit connection hole 24, which is a through hole for connecting theexternal terminal 20 to an external circuit via a screw or the like, isprovided on the other side of the plate portion 22.

The connecting pins 21 are provided in the plate portion 22 so as to beinsertable into a corresponding one of the cylindrical external terminalcommunication sections 8 a and 8 b of the main circuits. The connectingpins 21 are connected to the corresponding cylindrical external terminalcommunication sections by press fitting that is press-in connection. Forthis reason, the connecting pins 21 are each provided with a hole 25that provides a resilient characteristic (hereinafter, referred to as aresilient characteristic providing hole).

In the present embodiment, the external terminal 20 includes theconnecting pins 21 and the plate portion 22, which are separatecomponents. The external terminal 20 is formed by connecting theconnecting pins 21 to the relay communication holes 23 of the plateportion 22. For this reason, the connecting pins 21 can be formed of amaterial having a resilient characteristic, and the plate portion 22 canbe formed of a material having high electrical conductivity. Forexample, the material having a resilient characteristic is phosphorbronze, and the material having a high electrical conductivity iscopper.

That is, the material having a resilient characteristic such as phosphorbronze, whose electrical conductivity is less than copper or the like,is used only for the connecting pins 21. As a result, the resistance ofthe external terminals to be connected to the main circuits can bereduced.

As for the power semiconductor device 200 of the present embodiment, amethod for joining the external terminals 20 to the cylindrical externalterminal communication sections 8 a and 8 b of the main circuits, is theone in which the connecting pins 21 are attached to the plate portions22 in advance and then the connecting pins 21 are inserted into thecylindrical external terminal communication sections, or the one inwhich the connecting pins 21 are inserted into the cylindrical externalterminal communication sections in advance and then the connecting pins21 are connected to the plate portions 22.

In the power semiconductor device 200 of the present embodiment, theexternal terminals 20, in each of which multiple connecting pins 21 arearranged two-dimensionally in the single plate portion 22, are connectedto the cylindrical external terminal communication sections 8 a and 8 bjoined to the respective main circuits.

Accordingly, even if the external terminals 20 to be used for the powersemiconductor device 200 of the present embodiment are large terminalsto which a large current can be applied, the stress, which occurs due tothe joining of the external terminals 20 to the cylindrical externalterminal communication sections 8 a and 8 b of the main circuits, isdispersed and reduced. This prevents defects of the cylindrical externalterminal communication sections due to the stress, such as, anoccurrence of a gap at a joint surface between the outer side surface ofa cylindrical external terminal communication section and the transfermolding resin 9, or an occurrence of fine cracks in the transfer moldingresin 9. Consequently, high yield and excellent productivity inmanufacturing, and also excellent reliability, can be realized.

The external terminal communication sections are cylindrical externalterminal communication sections that do not have screw threads.Accordingly, the connection of the external terminals to the cylindricalexternal terminal communication sections is not thread connection. As aresult, the stress that occurs due to the connection of the externalterminals is further reduced.

In the present embodiment, the external terminals 20, in each of whichfour connecting pins 21 are two-dimensionally arranged in the singleplate portion 22, are used. However, the number of cylindrical externalterminal communication sections included in each of the cylindricalexternal terminal communication sections 8 a and 8 b may be more thanfour, and external terminals, in each of which more than four connectingpins are two-dimensionally arranged in the single plate portion, may beused.

In the case where the cylindrical external terminal communicationsections 8 a and 8 b each include three cylindrical external terminalcommunication sections, these three cylindrical external terminalcommunication sections may be arranged at the vertexes of a triangle,respectively, and also, in each external terminal, three connecting pinsmay be arranged, in the single plate portion, at the vertexes of atriangle, respectively.

Further, in the present embodiment, the material having a resilientcharacteristic is used for the connecting pins 21, and the externalterminals 20 are connected to the cylindrical external terminalcommunication sections by press fitting. However, a material having highelectrical conductivity may be used for the connecting pins 21, and thecylindrical external terminal communication sections and the externalterminals 20 may be joined by soldering. In this case, the resistance ofthe external terminals can be further reduced.

Third Embodiment

FIG. 7A is a schematic top view showing an external terminal 26 havingfour connecting pins to be connected to the cylindrical externalterminal communication sections of each main circuit of a powersemiconductor device according to the third embodiment of the presentinvention. FIG. 7B is a schematic cross-sectional view which is cutalong a line D-D indicated in the schematic top view of FIG. 7A.

Here, a surface of the plate portion 22 of the external terminal 26,which is the opposite surface to a surface having connecting pins 21protruding therefrom, is referred to as a top surface.

The power semiconductor device of the present embodiment (not shown) isthe same as the power semiconductor device 200 of the second embodimentexcept that external terminals 26, each of which has four connectingpins 21 and in each of which the plate portion 22 and the connectingpins 21 are integrated, are used.

As shown in FIGS. 7A and 7B, in each external terminal 26 of the presentembodiment, the connecting pins 21 are formed by performing a bendingprocess or the like on a metal plate of the plate portion 22. Also,similarly to the external terminals 20 of the second embodiment, theplate portion 22 of each external terminal 26 is provided with theexternal circuit connection hole 24, and the connecting pins 21 are eachprovided with the resilient characteristic providing hole 25.

The present embodiment provides the same effect as that of the secondembodiment. In addition, the external terminals 26 have highproductivity since, in each external terminal 26, the connecting pins 21are formed by performing the bending process on the metal plate of theplate portion 22.

In the present embodiment, when the external terminals 26 are eachformed of a single metal plate having a resilient characteristic, theexternal terminals 26 can be connected to the cylindrical externalterminal communication sections by press fitting although the resistanceof the external terminals becomes relatively high. When the externalterminals 26 are each formed of a single metal plate having highelectrical conductivity, the external terminals 26 can be connected tothe cylindrical external terminal communication sections by soldering,and the resistance of the external terminals 26 can be further reduced.

Fourth Embodiment

FIG. 8 is a schematic top view of a main body of a power semiconductordevice according to the fourth embodiment of the present invention.

FIG. 9 shows a circuit configuration of the main body of the powersemiconductor device according to the fourth embodiment of the presentinvention.

A power semiconductor device main body 50 of the present embodiment is aresult of sealing power semiconductor elements with the transfer moldingresin 9. Here, a surface of the transfer molding resin 9, at which holesof cylindrical external terminal communication sections are present, isreferred to as a top surface.

As shown in FIGS. 8 and 9, the power semiconductor device main body 50includes: a plurality of DC-side positive-electrode-side cylindricalexternal terminal communication sections 8e electrically connected tothe positive electrode of a positive-electrode-side power semiconductorelement 4 a; a plurality of DC-side negative-electrode-side cylindricalexternal terminal communication sections 8 f electrically connected tothe negative electrode of a negative-electrode-side power semiconductorelement 4 b; a plurality of AC-side cylindrical external terminalcommunication sections 8 g electrically connected to a connectionbetween the negative electrode of the positive-electrode-side powersemiconductor element 4 a and the positive electrode of thenegative-electrode-side power semiconductor element 4 b; a pair ofcontrol-electrode-use cylindrical external terminal communicationsections 8 h and 8 i electrically connected to the control electrode ofthe positive-electrode-side power semiconductor element 4 a; and a pairof control-electrode-use cylindrical external terminal communicationsections 8 j and 8 k electrically connected to the control electrode ofthe negative-electrode-side power semiconductor element 4 b.

The positive-electrode-side cylindrical external terminal communicationsections 8 e and the negative-electrode-side cylindrical externalterminal communication sections 8 f constitute a DC-side cylindricalexternal terminal communication section 8 n.

Further, the plurality of AC-side cylindrical external terminalcommunication sections 8 g are arranged two-dimensionally, and holes ofthe AC-side cylindrical external terminal communication sections 8 g arepresent at the top surface of the transfer molding resin 9.

There are two DC-side positive-electrode-side cylindrical externalterminal communication sections 8 e and two DC-sidenegative-electrode-side cylindrical external terminal communicationsections 8 f. The DC-side cylindrical external terminal communicationsections 8 n including the both is arranged two-dimensionally. Holes ofthe DC-side cylindrical external terminal communication sections 8 n arealso present at the top surface of the transfer molding resin 9.

The power semiconductor device main body 50 according to the presentembodiment is a fundamental form of a power electronics apparatus suchas an inverter.

FIG. 10 is a schematic top view of the power semiconductor deviceaccording to the fourth embodiment of the present invention, the mainbody of which includes external wiring to be connected to an externalcircuit.

FIG. 11 is a schematic cross sectional view of the power semiconductordevice shown in FIG. 10, which is cut along a line E-E indicated in theschematic top view of FIG. 10.

As shown in FIGS. 10 and 11, the power semiconductor device main body 50of a power semiconductor device 300 of the present embodiment isprovided with external wiring to be connected to an external circuit. Tobe specific, the power semiconductor device main body 50 is providedwith: a positive-electrode-side wiring board 31 and anegative-electrode-side wiring board 32, with which a DC-side wiringsubstrate 30 is formed; an AC-side external terminal 34; and a controlsubstrate 35.

Through the connecting pins 21, the positive-electrode-side wiring board31 is connected to the positive-electrode-side cylindrical externalterminal communication sections 8 e; the negative-electrode-side wiringboard 32 is connected to the negative-electrode-side cylindricalexternal terminal communication sections 8 f; the AC-side externalterminal 34 is connected to the AC-side cylindrical external terminalcommunication sections 8 g; and the control substrate 35 is connected tothe control-electrode-use cylindrical external terminal communicationsections 8 h, 8 i, 8 j and 8 k.

The DC-side wiring substrate 30 is formed by integrating thepositive-electrode-side wiring board 31 and the negative-electrode-sidewiring board 32 with an insulation layer 33 interposed therebetween.

A plate portion of the AC-side external terminal 34 is provided with theexternal circuit connection hole 24 for connecting the AC-side externalterminal 34 to an external circuit.

The control substrate 35 includes a drive circuit for thepositive-electrode-side power semiconductor element 4 a and thenegative-electrode-side power semiconductor element 4 b.

Here, connection of the positive-electrode-side wiring board 31 and thenegative-electrode-side wiring board 32, which are plate portions of theDC-side wiring substrate 30, to the connecting pins 21, and connectionof the plate portion of the AC-side external terminal 34 to theconnecting pins 21, are formed by soldering or brazing, for example.

In the present embodiment, the AC-side external terminal 34 has fourconnecting pins 21 which are two-dimensionally arranged. The AC-sideexternal terminal 34 is connected to the AC-side cylindrical externalterminal communication sections 8 g via these connecting pins 21.Therefore, similarly to the power semiconductor device of the secondembodiment, by connecting the AC-side external terminal 34 to theAC-side cylindrical external terminal communication sections 8 g, thestress applied to the AC-side cylindrical external terminalcommunication sections 8 g can be dispersed and reduced, whereby defectsof the AC-side cylindrical external terminal communication sections 8 gcan be prevented.

The AC-side cylindrical external terminal communication sections 8 g andthe connecting pins 21 are connected by, for example, press-inconnection such as press fitting, or soldering.

The positive-electrode-side wiring board 31 is connected to thepositive-electrode-side cylindrical external terminal communicationsections 8 e via the two connecting pins 21 that are aligned. Also, thenegative-electrode-side wiring board 32 is connected to thenegative-electrode-side cylindrical external terminal communicationsections 8 f via the two connecting pins 21 that are aligned. TheDC-side wiring substrate 30 is formed by integrating thepositive-electrode-side wiring board 31 and the negative-electrode-sidewiring board 32 via the insulation layer 33.

In other words, four connecting pins 21, which are the two connectingpins 21 provided in the positive-electrode-side wiring board 31 and thetwo connecting pins 21 provided in the negative-electrode-side wiringboard 32, are two-dimensionally arranged in the DC-side wiring substrate30. The DC-side wiring substrate 30 is connected to the DC-sidecylindrical external terminal communication sections 8 n via these fourconnecting pins 21 that are two-dimensionally arranged. With thisstructure, similarly to the power semiconductor device of the secondembodiment, by connecting the DC-side wiring substrate 30 to the DC-sidecylindrical external terminal communication sections 8 n, the stressapplied to the DC-side cylindrical external terminal communicationsections 8 n can be dispersed and reduced, and defects of the DC-sidecylindrical external terminal communication sections 8 n can beprevented.

Thus, since the power semiconductor device 300 of the present embodimentprevents defects from occurring at the cylindrical external terminalcommunication sections, the manufacturing yield thereof is high, and theproductivity and reliability thereof are excellent.

Further, in the present embodiment, the positive-electrode-side wiringboard 31 and the negative-electrode-side wiring board 32 for forming theDC-side wiring substrate 30 are connected to the DC-side cylindricalexternal terminal communication sections 8 n via the connecting pins 21.For this connection, press-in connection such as press fitting,soldering, or the like is used. The connection by these methods reduces,as compared to thread connection, the inductance of a circuit connectingthe DC-side wiring substrate 30, which is a DC-side circuit, to thepositive-electrode-side power semiconductor element 4 a and thenegative-electrode-side power semiconductor element 4 b.

For this reason, a surge voltage, which occurs due to wiring inductancewhen a large current applied to the power semiconductor device is cutoff, can be reduced.

In the present embodiment, the plate portions of the AC-side externalterminal 34 and the DC-side wiring substrate 30 are separate componentsfrom the connecting pins 21 thereof. Accordingly, the plate portions maybe formed of metal having high electrical conductivity and theconnecting pins may be formed of metal having a resilientcharacteristic, or the plate portions and the connecting pins may beboth formed of metal having high electrical conductivity.

Alternatively, each plate portion and the connecting pins 21 thereof maybe integrally formed of a single piece of metal.

In the present embodiment, the configuration of a circuit to be set in amold is not limited to the one shown in FIG. 9. For example, threecircuits each having the configuration shown in FIG. 9 may be connectedin parallel at the positive electrode side and at the negative electrodeside, i.e., a three-phase inverter configuration.

The power semiconductor device according to the present invention issmall in size, capable of operating with a large current, and excellentin terms of productivity and reliability, and therefore effectivelyutilized in electric appliances that are required to be high-performanceand low-cost.

Various modifications and alterations of this invention will be apparentto those skilled in the art without departing from the scope and spiritof this invention, and it should be understood that this is not limitedto the illustrative embodiments set forth herein.

What is claimed is:
 1. A power semiconductor device comprising: acircuit substrate including a metal heat sink and including a thermalconductive insulation layer joined to one surface of the metal heat sinkand including wiring patterns provided on a surface of the thermalconductive insulation layer, which surface is opposite to a surface, ofthe thermal conductive insulation layer, joined to the metal heat sink;power semiconductor elements joined to the wiring patterns; cylindricalexternal terminal communication sections joined to the wiring patternsand including holes exposed at a top surface of a transfer molding resinrespectively having a flat vertical inner surface on a cross-section ofthe cylindrical external terminal communication section in a directionperpendicular to the wiring patterns; and wiring means for establishingconduction between the power semiconductor elements, between the wiringpatterns, and between the power semiconductor elements and the wiringpatterns, the circuit substrate, the power semiconductor elements, thecylindrical external terminal communication sections, and the wiringmeans, all being sealed with the transfer molding resin, wherein thecylindrical external terminal communication sections are joined to thewiring patterns so as to be substantially perpendicular to the wiringpatterns, such that a plurality of cylindrical external terminalcommunication sections among the cylindrical external terminalcommunication sections are two-dimensionally arranged on each of wiringpatterns that act as main circuits, and external terminals areinsertable and connectable to the holes of the cylindrical externalcommunication sections.
 2. The power semiconductor device according toclaim 1, wherein an external terminal formed with a plate portion and aplurality of connecting pins arranged two-dimensionally in the plateportion is connected to the plurality of cylindrical external terminalcommunication sections arranged on each of the main circuits.
 3. Thepower semiconductor device according to claim 2, wherein the plateportion of the external terminal is a separate component from theconnecting pins thereof, the plate portion is formed of metal, and theconnecting pins are each formed to make a press-in connection with oneof the cylindrical external communication sections.
 4. The powersemiconductor device according to claim 2, wherein the plate portion ofthe external terminal is a separate component from the connecting pinsthereof, and the plate portion and the connecting pins are each formedof metal.
 5. The power semiconductor device according to claim 2,wherein the plate portion and the connecting pins of the externalterminal are integrally formed of a single piece of metal.
 6. The powersemiconductor device according to claim 2, wherein a hole is included ineach of the connecting pins.
 7. The power semiconductor device accordingto claim 1, wherein an inner diameter of a top portion of eachcylindrical external terminal communication section is greater than aninner diameter of a central portion of the respective cylindricalexternal terminal communication section.